There are six persons A, B, C, D, E and F. C is the sister of F. B is the brother of E's husband. D is the father of A and the grandfather of F. There are exactly two fathers, three brothers and one mother in the group. How many male members are there in the group?

Introduction / Context:
This reasoning problem combines relationship clues with a count condition: the group contains exactly two fathers, three brothers and one mother. You are asked to determine how many male members are present. Solving it requires you to propose a consistent family structure that satisfies all relational clues and then see how many people must be male in that structure.

Given Data / Assumptions:

• C is the sister of F, so C is female and F is C's sibling.
• B is the brother of E's husband, so B is male and E's husband is also male.
• D is the father of A and the grandfather of F, so D is male, A is a child of D, and F is a grandchild of D.
• There are exactly two fathers in the group.
• There are exactly three brothers in the group.
• There is exactly one mother in the group.

Concept / Approach:
The usual way to tackle this kind of puzzle is to try to construct a specific family arrangement that matches all conditions. A particularly natural arrangement is one where D is the father of A, A is the father of F and C, and E is A's wife (the only mother). B is then the brother of A (E's husband), and together A, B and F form the three brothers. Once such a structure is found, you can count how many male members it has and verify that it satisfies the father and mother counts.

Step-by-Step Solution:
Step 1: From D is the father of A and the grandfather of F, conclude that A is a child of D and that F is a child of one of D's children.Step 2: A simple fit is to make A the parent of F. Then the chain is D (grandfather) → A (father) → F (child).Step 3: Since C is the sister of F, C is another child of A (sharing the same parents) and is female.Step 4: There are exactly two fathers. D is one father (of A), and A is the other father (of F and C). No other male in the group can be a father without violating this count.Step 5: There must be exactly one mother. Let E be A's wife and the mother of F and C. Then E is the single mother in the group.Step 6: From B is the brother of E's husband, and E's husband is A, it follows that B is A's brother. So A, B and F are three males who are each a brother of someone, satisfying the three brothers condition.

Verification / Alternative check:
Summarise the assignments: D is male and father of A; A is male, husband of E and father of F and C; E is female and mother of F and C; F is male (brother of C); C is female (sister of F); B is male (brother of A). Two fathers are D and A. One mother is E. Three brothers are A (brother of B), B (brother of A) and F (brother of C). This satisfies every given condition exactly. The male members are D, A, B and F, so there are four males and two females (C and E). Any attempt to assign different genders (for example, making B or F female) breaks one of the brother or father counts.

Why Other Options Are Wrong:
1 or 2 male members cannot support two fathers and three brothers at the same time.3 male members would be insufficient to have three distinct brothers plus two fathers without overlapping roles incorrectly.5 male members would force more than one mother or alter the sibling structure, contradicting the given counts.

Common Pitfalls:
It is easy to miscount fathers by allowing E's husband or D's other children to also become fathers inside the group. Another mistake is ignoring the requirement that there is only one mother and accidentally giving the role of mother to both C and E. To avoid this, always start with the fixed roles (father, sister, brother) and then deliberately assign exactly the required number of fathers, brothers and mothers, without adding extra parents.

Final Answer:
In a valid family structure that satisfies all conditions, there are 4 male members in the group.